Geoengineering may be a good idea. Then again, it may destroy the planet.

There’s a concept that is being researched called geoengineering that would try to repair damage to the environment through artificial means. Supporters say it’s the only way to prevent a cataclysmic end to the planet. Detractors say it will bring that end closer to reality.

If global warming really takes off, some researchers think we should consider pumping sulfate aerosols high up in the atmosphere to shade the earth and cool it back down. The approach, one of a group of strategies known as geoengineering, sounds mad. But it has the attraction of being cheap. According to one estimate, it would cost less than a billion dollars a year, pocket change in a world economy of $70 trillion (see “A Cheap and Easy Plan to Stop Global Warming” and “Climate Change: The Moral Choices”).